In accordance with a recent progress of an electronics technology, electronic equipment and communication equipment are getting more highly functional and more reduced in size. Under such circumstances, as a method of mounting, for example, semiconductors on a wiring board, a bare chip mounting method instead of package mounting has come into practical use for realizing higher mounting density. Further, passive components such as a capacitor and a resistor of a chip-mounted type have been reduced in size to 0.6 mm×0.3 mm (0603).
As a method for electrical connection between wiring layers (interlayer connection) in the wiring board itself, a method of using conductive layers formed in inner surfaces of through holes is being replaced by a method in which blind vias are formed for respective layers by CO2 laser or UV-YAG laser and the blind vias are plated on inner surfaces thereof or filled with conductive paste. Further, as a method of forming wiring patterns, since they are getting more microscopic, an etching method (subtractive process) is being replaced by a method of forming the wiring by metallization through plating (additive process). This has achieved microscopic formation at a level of L/S (line/space)=about 20 μm/20 μm.
For still higher component mounting density and still reduced size of equipment under such circumstances, for example, a component built-in wiring board in which a component is incorporated in a wiring board is usable. For example, Japanese Utility Model Laid-open No. Hei 5-53269 discloses such a component built-in wiring board.